Process of recovering supersaturants



July 14, 1931.

| H. DUSCHAK PROCESS OF RECOVERING' SUPERSATURANTS Filed Oct. 10, 1927 5:50 ckxs 741.5

401v: cavm/M/A/a era/awn czwmu FILTER- TH/CKfA/Ek INVENTOR B llo/vel H Base/70k A TTO NE YS Patented July 14, 1931 UNITED. STATES PATENT OFFICE LIONELH. DUSCHAK, F BERKELEY, CALIFORNIA, ASSIGNOR TO BURNHAM CHEMICAL COMPANY, OF WESTEND, CALIFORNIA, A CORPORATION OF NEVADA PROCESS or nncovnnrne SUPERSA'IURANTS Application filed October 10, 1927. Seria1No.225,375.

My invention relates to the recovery from solutlons, partlcularly brines, of substances With which the solution is supersaturated and is particularly adaptable to the procuring of 5 borax crystals frombrine such as that found at "Searles Lake, California. Such brines have been variously treated to recover crystallized salts and supersaturants therefrom and'in several patents to George B. Burnham there is disclosed a manner of obtain ing these substances by the agitation of supersaturated Searles Lake brine. While'it is possible to recover a large percentage of the crystals and some of the supersaturant by 1 the employment of such methods, it is not feasible to obtain all of the crystals or substantially all of the supersaturant or supersaturants.

It is therefore an object ofmy invention,

to provide a process by which substantially all of the available crystals and supersaturants are obtained from, a supersaturated solution. a

' Another object of my invention is to provide a process of obtaining crystallized and supersaturating 'borax which can be continuously operated.

A further object of my invention is to provide an ample source of borax crystals to be used as seed in promoting the formation of further borax crystals from a supersaturated brine.

My invention possesses other advantageous features some of which with the foregoing Will be set forth at length in the following description where I shall outline in full the preferred form of the process of my in- Vention. I a

The drawing is a diagrammatic representation of the process of my invention.

' In its preferred form, my process preferably comprises treating a supersaturated brine so that crystals are formed therein and removing a large part of such crystals in a preliminary operation, then further treating the brine to remove the balance of the crystals and substantially all of the supersatw rant, also preferably utilizing some of the crystals obtained in the further treatment as seed in the initial treatment to accelerate the formation of the initial crop of crystals from the brine.

lVhile my process is by no means confined to the procuring of borax crystals, it is Well adapted to such a use and for convenience is so described herein. Brine, such as that obtained at Searles' Lake, can be concentrated in a number of different ways until it is supersaturated. As disclosedin the Burnham patents, referred to above, the brine is very often exposed to the action of the sun and ind in open ponds of considerable extent until the brine becomes supersaturated with borax. It is this supersaturated brine that is employed in my process. I first subject the brine to agitation in order to cause or start the formation of crystals the supersaturated solution.

"To this end, supersaturated brine is conducted from the evaporating pond into a thickener 60f the conventional kind in which is installed an agitator 7. The agitation of the brine initiates the formation of borax crystals. These crystals are continuously gathered to the outlet 8 of the thickener and comprisealarge part, usually amfajority, of the crystals available in the brine. The deposited crystals discharged from the thickener 6 are available for further treatment, if

tation of brine with seed crystals is effective to relieve supersaturation, the process is not as complete or rapld as is desired. This is apparently because the brine is somewhat visof bor'aX from cous and each seed crystal is surrounded with an envelope which must be penetrated before the supersaturant' can crystallize and deposit thereon. I therefore treat the brine further,

not only to remove almost entirely, the" crystals already formed, but also to cause the. crystallization and recovery of substantially all of the substance supersaturating the brine.

For this purpose I provide around thepe riphery ofthe thickener an overflow launder 9'of the usual type which receives overflow ing brine from which a large partof the borax The suction can be eiiected-bysuitab'l e machinery or the gravital action of the fluid may be employed alone. As the brine from the onta er 2.12a sesthr t e lowly fi q ving' drum 13, it deposits residual crystals of borax upon the surface of the drum. The treated brine from which substantially all of the available borax crystals have been extracted passes out thru a discharge pipe 14, which, conveniently, can lead back into; an evaporating pond forf'urther evaporation to another supersaturation with borax.

D i g t pr gress of my proce s, e borax crystals deposit upon the'surface of drum 13, in increasing amounts and form a cake or layer of borax crystals. This filter cake of borax crystalsis exceedingly valuable in removingga large partof the supersaturant, in this case borax ,'f r01;n the brine passing thru the drum 18. The interstices of minute extent between the deposited crystalsnot only serve. as excellent filters for the interception' 'of additional borax crystals but, apparently due to the scouring action of the brine, the filter cake acts; as. a seed bed to cause the crystallization and precipitation of'substantially all of the supersaturant. There is; thus a mechanical filtration or separation of the crystallized borax and also, a'seeding effect due to the large honey combed cake of borax; on which deposit crystals, which prior to my invention remained uncrystallized in the supersaturated solution. For these reasons a very large proportion of the total borax available in the, brine is extracted and deposited as crystals on the surface of thed f lm 13. When the process has been in effect for some period and 'a cake of the desired thickness has built up upon the drum 13, any excess of crystals is preferably removed by a scraper 16 remainingstationary with respect, to the drum a d beari g agai st. he. accumul t d cake thereon so that crystals extending radially twa r gi en. max mum ar rape off and are Withdrawn by suitable means 1'( to a convenient point of recovery.

I"ca .,vQ ie u seemploy ol ly the d m fi ter o enha ce rysta lizat on, and rem v th bores fr m the. brine b t inasmu h. s i

process is somewhat slower than that of agi-v tation, the crystal recovery is rendered commer ially fe ble pr marily y e process of mv inven io n wh iehth maj r portio of the crystals available is first extracted simply by agitation and the residue together with additional crystals is then removed by the drum filter. By the combination of these two methods of producing and removing the bor'a'x' crystals which act as seed. As a convenient su )ply of approximately pure seed crystals I iv e rt, if desired, a portion of the residual crystals obtained from the revolv ing drum l3 and conduct them, as at 18,,back to'thethickener 6v into which they'are intro: duced for the purpose of accelerating the formation ofjborax crystals, from thef super-v saturated brine undergoing agitation therein, Invthis manner, a certain'proportion of thecrystals, is always undergoing'a continuous cycle from the thickener to the drum filter and back to the thickener asseed, while as long as brine is introduced into the thickener I am,- enabled to, take borax crystals thru the outlet 8 and from'the discharge 17 The rocess of my invention therefore p.05.- sesses t he virtues'of the agitation means vof removing crystal linasmuch asitis relatively rapid and in addition obtains, the advantageof being thorough and extracts substantially all of the available borax from the brine due. to the effective filtering thru the revolving filter drum 13 Other apparatus than that described can of course be employed toeffeet the process of my invention and that shown in the accompanying diagram is purely illustrative as the apparatus can be varied considerably without afi'ecting adversely the results of my process.

I la m:

1. A process of recovering a supersaturant comprising agitating supersaturated brine to promote crystallization, removing crystals from the brine, passing the remaining brine through a filter cake of similar crystals; to remo addi ona ry a s fr m id b ine: an using some of said additional, crystals as seed in brine being agitated.

V 2. A process of recovering a snpersaturant comprising supersaturated brine,'remo,vin'g ub tant a por ion of e re ul ing, ystal therefrom, and passing, the remaining brine through a cake ofsimilar crystals to remove substantially the remainder of the resul li lg yst 4 v 3, A process of removing a supersaturant from brine supersaturated with borax comprising agitating the brine to crystallizeout borax, separating a, majority of the borax c ys al from the bri d passi g th rue-i main ng br n thr ugh a ke. o r rys: tals.

4. A process of removing a supersaturant from brine supersaturated with boraX comprising seeding the brine to promote the formation of borax crystals, removing some of o the borax crystals from the brine, passing the remaining brine through a cake of borax crystals to remove others of the borax crystals from said brine, and using crystals from said cake for seeding brine.

m 5. A process of removing a supersaturant from brine supersaturated with borax comprising agitating the brine in the presence of seed crystals to promote the formation of borax crystals, removing borax crystals from said brine, passing the remaining brine through a filter cake of borax crystals, and using crystals deposited on said cake for seeding brine being treated.

6. A process of removing a supersaturant from brine comprising agitating the brine to form crystals, removing most of said crystals, and passing the remaining brine through a filter cake to promote additional crystallization upon the crystals in said cake.

7. A process of removing a supersaturant from brine comprising treating said brine to form crystals, removing most of said crystals, and passing said brine through a filter cake on which other crystalline matter is formed and deposited.

8. A process of removing supersaturated borax from brine supersaturated with borax comprising agitating the brine in the presence of seed crystals of borax to promote the formation of borax crystals and the growth of said seed crystals, removing borax crystals from said brine, passing the remaining brine through a filter cake of borax crystals, and using the crystals deposited on said cake for 40 seeding brine passing through said filter thereby crystallizing substantially the remaining supersaturated borax from said brine.

9. A process of recovering from a supersaturated brine a supersaturated salt,-co1nprising filtering said supersaturated brine through a filter composed substantially of crystals of said supersaturated salt and removing said crystals from said filter when said filter attains a predetermined size.

10. A process of removing a supersaturant from a supersaturated brine comprising passing said brine through a mass of substantially the crystals of said supersaturant whereby the crystals of said supersaturant are substantially removed, and whereby further crystallization of said supersaturant occurs on said mass of crystals.

In testimony whereof, I hereunto set my hand.

LIONEL H. DUSCHAK. 

